Debunk claim:

There is evidence of regular Russian army forces operating in Donbas, including video and photos from Russian soldiers and pro-Russian sources showing Russian soldiers and equipment operated exclusively by the Russian military in Donbas. Polygraph. info documented proof of Russia sending tanks into Donbas.https://www.bellingcat.com/resources/2015/05/28/tankspotting-how-to-identify-the-t-72b3/, https://www.youtube.com/watch?v=2zssIFN2mso, http://www.polygraph.info/a/russia-kremlin-ukraine-donbas-tanks/28308649.html. Further debunking at Polygraphhttp://www.polygraph.info/a/russia-ukraine-military-presence-kremlin/28340880.html